Recording head and recording apparatus, and inspection apparatus of recording head and method thereof

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a recording head and a recording apparatus, which applies thermal energy to a liquid and discharges the liquid through a nozzle, and an inspection apparatus of the recording head and a method thereof.

2. Description of the Related Art

An inkjet recording apparatus, e.g., an inkjet printer, prints a variety of types of data by discharging ink through nozzles that are built into a recording head, e.g., an inkjet head, thus causing the ink to adhere to a sheet of printing paper or other recording material. Such an inkjet printer has many advantages, including making little noise, being capable of high-speed printing, and being usable with a wide range of recording material. Among the inkjet heads, a type of inkjet head that applies thermal energy to the ink when discharging the ink through the nozzle has such advantages as being very responsive to a print signal and lending itself easily to high-density integration (see U.S. Pat. No. 4,723,129 and U.S. Pat. No. 4,740,796).

The inkjet printer that uses such an inkjet head, on the other hand, is prone to experiencing a discharge malfunction with some or all of the inkjet heads, whether due to the nozzle being clogged by a foreign substance, an air bubble interfering with an ink supply path, or a change in a wetness level (wettability) of a nozzle surface, among other causes. Particularly where high-speed printing is concerned, when using a full-line type of inkjet head, upon which is mounted a plurality of nozzles, corresponding to a full width of the recording material, an important issue that has emerged is that of identifying the nozzle among the plurality of nozzles where the discharge malfunction has occurred, providing for compensation of a portion of an image corresponding to the malfunctioning nozzle, and taking the compensation into account in a recovery process of the inkjet head. The inkjet printer that employs such an inkjet head also suffers from a situation wherein a quantity of ink that is discharged from each respective nozzle may change in conjunction with a temperature change in the inkjet head, and a density of the printed image will not be reliable. It is particularly crucial where the full-line type of inkjet head is concerned to curb a degradation of the image that might result from such a change in the quantity of ink discharged.

In view of the foregoing crucial factors, a variety of types of methods for detecting when the ink is not being discharged, compensating for failure to discharge, control methods and apparatuses, and a variety of methods for controlling the quantity of ink discharged have long been promulgated.

Japanese Examined Patent Publication No. H04-006549 discloses a method that detects, in an ink discharge source, whether or not the ink is being discharged. According to the document, a conductor, the resistance thereof changes in response to heat, is placed in a position from which it can detect the heat that is emitted by an electrothermal transducer, i.e., a heater, and an application of the discharge signal to the electrothermal transducer controlled in response to a change in temperature as signified by a degree of change in a value of the resistance of the conductor.

Another method that detects, in an ink discharge source, whether or not the ink is being discharged is disclosed in Japanese Patent No. 2,831,778, wherein is disclosed an inkjet heard wherein the electrothermal transducer (heater) and a temperature sensor are both mounted on a silicon wafer or other support, and a temperature sensor that is configured of a film is overlaid with an array region of the electrothermal transducer. Japanese Patent No. 2,831,778 further discloses that the array region of the heaters is completely contained within an array region of the temperature sensor, which in turn is positioned as an overlay of the array of the heaters, thus improving the precision and the responsiveness of the detection and the control of the temperature.

Japanese Patent Laid Open No. 2002-178492 discloses a technique of detecting a temperature attribute of the inkjet head by determining a threshold value of detecting a remaining quantity of the ink in accordance with the temperature change that occurs when a specified energy is applied to a heater of the inkjet head.

As a proposal concerning each respective type of discharge malfunction determination criterion or condition for the purpose of improving the precision of the temperature detection, it has been suggested that the inkjet head be protected from an excessive increase in heat, for example, and performing a high-precision detection of a discharge malfunction. According to the proposal, Japanese Patent Laid Open No. H07-052408, a ranking of the inkjet head is performed according to a value of a resistance of a dummy resistor, and the determination condition of whether or not a discharge malfunction has occurred is changed according to the ranking.

As an inspection method that detects an ink discharge status of the inkjet head, there is an inspection method disclosed in Japanese Patent Laid Open No. H11-138788, wherein a temperature increase and a temperature decrease are measured commensurate with a level of heat increase that does not allow the ink discharge, and the temperature increase and the temperature decrease of the inkjet head are measured on a timing different from a timing of a print operation, pertaining to a preparatory ink discharge. If the ink discharge malfunctions, the temperature increase and the temperature decrease of the inkjet head are measured, a heat attribute of the inkjet head is provisionally obtained according to a print status monitoring step, and a determination is made as to whether or not the ink is being properly discharged from the inkjet head, in accordance with a result of a comparison of the measurements.

Neither Japanese Examined Patent Publication No. H04-006549 nor Japanese Patent No. 2,831,778 disclose specifying the position of each respective nozzle of a discharge malfunction. Nor is each respective detection circuit that detects the degree of change in the value of the resistance according to the heat that is emitted by the electrothermal transducer made clear. Consequently, it is not possible to identify the nozzle that is experiencing the discharge malfunction.

The conventional examples of Japanese Patent Laid Open Nos. 2002-178492, H07-052408 and H11-138788 do not disclose a technique of detection pertaining to multiple nozzles, given that they focus on detecting the discharge malfunction on a per inkjet head basis. Accordingly, there is no mention of identifying the malfunctioning nozzle of the inkjet head. Given that the threshold is computed solely from a detected thermal attribute, no consideration has been given to a precision in detection that corresponds to an electrical attribute or a plurality of different thermal attributes. The inkjet printer in Japanese Patent Laid Open No. H07-052408 employs a ranking based on the heater attribute of the dummy resistance. The ranking substitutes a select thermal attribute with the electrical attribute, however, and thus, does not have the improvement of improving the precision in detection based on the detected value of the thermal attribute as its objective.

Therefore, it would be desirable to solve the foregoing problems indigenous to the conventional technology.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a technology is offered that corrects the temperature data that is detected by the temperature sensor that corresponds to each respective nozzle of a recording head, and corrects an electrical or a thermal misalignment in each respective temperature sensor.

According to another aspect of the present invention, a technology is offered that appropriately determines a timing for detecting an occurrence of a fault in each respective nozzle of the recording head, and detects whether or not a fault is present in the recording head, according to the timing.

According to an aspect of the present invention, there is provided a recording apparatus for recording an image using a recording head that affects ink with thermal energy from a plurality of electrothermal transducers to discharge the ink via a nozzle. The recording head includes a plurality of temperature sensors, each of which is respectively positioned in correspondence with each electrothermal transducer; and a temperature detection circuit configured to select each one of the plurality of temperature sensors and obtain temperature data detected by the selected temperature sensor. The recording apparatus includes a first temperature detection unit, in a state that a first electrothermal transducer is not driven with an electric current, configured to obtain first temperature data that the temperature sensor corresponding to the first electrothermal transducer detects by way of the temperature detection circuit; a second temperature detection unit, in a state that the first electrothermal transducer is driven with an electric current, configured to obtain second temperature data that the temperature sensor corresponding to the first electrothermal transducer detects by way of the temperature detection circuit; an acquisition unit that acquires correaction data for correcting the temperature data that the temperature sensor corresponding to the first electrothermal transducer detects, based on the first and the second temperature data obtained by the first and second temperature detection units; and a correaction unit configured to correct the temperature data that the temperature sensor corresponding to the first electrothermal transducer detects, in accordance with the correaction data acquired by the acquisition unit.

According to another aspect of the present invention, a recording head is provided for affecting ink with thermal energy from an electrothermal transducer to discharge the ink via a nozzle. The recording head includes a plurality of temperature sensors, each of which is respectively positioned in correspondence with each electrothermal transducer; a temperature detection circuit configured to select each of the plurality of temperature sensors, and obtain respective temperature data detected by the selected temperature sensor; a storage unit configured to store correaction data for correcting the temperature data detected by each of the plurality of temperature sensors; and a correaction unit configured to correct the temperature data detected by each of the plurality of temperature sensor in accordance with the correaction data stored in the storage unit.

Moreover, according to another aspect of the present invention a method is provided of inspecting a recording head for affecting ink with thermal energy from an electrothermal transducer to discharge the ink via a nozzle. The method includes flowing an electric current into a first electrothermal transducer and acquiring temperature data detected by a temperature sensor that is arranged in the recording head in correspondence with the first electrothermal transducer; detecting a first timing when the acquired temperature data reaches a peak temperature; detecting a second timing when a temperature change arises in conjunction with a shrinkage in a bubble that has emerged; setting each threshold for serving as a reference for determining whether or not a malfunction occurs at the first and second timings; and determining a driving status of the first electrothermal transducer based on the temperature data detected at the first and second timings by the temperature sensor corresponding to the first electrothermal transducer.

Furthermore, according to another aspect of the present invention, a device is provided for inspecting a recording head for affecting ink with thermal energy from an electrothermal transducer to discharge the ink via a nozzle. The device includes a measurement unit configured to flow an electric current into a first electrothermal transducer and acquire a temperature data detected by a temperature sensor that is respectively positioned in the recording head in correspondence with the first electrothermal transducer; a first detection unit configured to detect a first timing when the acquired temperature data reaches a peak temperature; a second detection unit configured detect a second timing when a temperature change arises in conjunction with a shrinkage in a bubble that has emerged; a setting unit configured to set each threshold for serving as a reference for determining whether or not a malfunction occurs at the first and second timings; and a determination unit configured to determine a driving status of the first electrothermal transducer, based on the temperature data detected at the first and second timings by the temperature sensor corresponding to the first electrothermal transducer.

Further features and aspects of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

<figref idrefs="DRAWINGS">FIG. 1</figref> depicts a view illustrating an example inkjet head according to an embodiment.

<figref idrefs="DRAWINGS">FIG. 2</figref> depicts an oblique cutaway view of the inkjet head depicted in <figref idrefs="DRAWINGS">FIG. 1</figref>.

<figref idrefs="DRAWINGS">FIG. 3</figref> depicts an oblique cutaway view of an example recording element unit.

<figref idrefs="DRAWINGS">FIG. 4A</figref> depicts a view illustrating an example configuration of a recording element board.

<figref idrefs="DRAWINGS">FIG. 4B</figref> depicts a cross-section view of the section labeled A-A in <figref idrefs="DRAWINGS">FIG. 4A</figref>.

<figref idrefs="DRAWINGS">FIG. 5A</figref> and <figref idrefs="DRAWINGS">FIG. 5B</figref> depict a cross-section view and a diagram, respectively, of the recording element unit of the inkjet head according to the embodiment, with the nozzle omitted.

<figref idrefs="DRAWINGS">FIG. 6</figref> depicts a plane view illustrating an example temperature sensor according to another embodiment of the present invention.

<figref idrefs="DRAWINGS">FIG. 7</figref> is a block diagram describing an example driving circuit and a temperature detection circuit of heaters of the inkjet head according to a first embodiment of the present invention.

<figref idrefs="DRAWINGS">FIG. 8</figref> is a timing chart describing an example of a timing of a control signal for driving the heater and obtaining a temperature data of the inkjet head according to the first embodiment of the present invention.

<figref idrefs="DRAWINGS">FIG. 9</figref> depicts a graph explaining a change in an output value of a temperature sensor, both when the inkjet head properly discharges ink, and with each respective discharge fault, according to the embodiment.

<figref idrefs="DRAWINGS">FIG. 10</figref> depicts a graph explaining that the temperature that the temperature sensor detects pertaining to the inkjet head varies depending on a thickness of an interlayer insulation film, according to the embodiment.

<figref idrefs="DRAWINGS">FIG. 11</figref> depicts a view of an exemplary full multi-inkjet printer that employs the inkjet head according to the embodiment.

<figref idrefs="DRAWINGS">FIG. 12</figref> is a block diagram describing an example configuration of an inkjet printer according to the embodiment.

<figref idrefs="DRAWINGS">FIG. 13</figref> is a flowchart explaining an example process according to the first embodiment.

<figref idrefs="DRAWINGS">FIGS. 14A through 14C</figref> depict graphs explaining a measurement of a temperature attribute of the inkjet head according to the embodiment.

<figref idrefs="DRAWINGS">FIG. 15</figref> is a flowchart explaining an example process according to a second embodiment.

<figref idrefs="DRAWINGS">FIG. 16</figref> depicts a view explaining an example of a heat timing according to the second embodiment of the present invention.

<figref idrefs="DRAWINGS">FIG. 17A</figref> and <figref idrefs="DRAWINGS">FIG. 17B</figref> depict views explaining a circumstance wherein a plurality of the measurement timings are set versus to a heater driving, according to the second embodiment.

<figref idrefs="DRAWINGS">FIG. 18</figref> depicts an example of a circuit diagram of an inkjet head according to a third embodiment of the present invention.

<figref idrefs="DRAWINGS">FIG. 19A</figref> depicts a view illustrating a configuration of the inkjet head according to the third embodiment.

<figref idrefs="DRAWINGS">FIG. 19B</figref> depicts a view explaining an output pertaining to an output terminal of each respective sensor, and a misalignment thereof, pertaining to the inkjet head depicted in <figref idrefs="DRAWINGS">FIG. 19A</figref>.

<figref idrefs="DRAWINGS">FIG. 20</figref> is a flowchart describing a calibration process of the inkjet head according to the third embodiment.

<figref idrefs="DRAWINGS">FIG. 21</figref> depicts a view explaining the electrical misalignment and an overall misalignment that are stored in a correaction unit, according to the third embodiment.

DESCRIPTION OF THE EMBODIMENTS

Various embodiments of the present invention will now herein be described below in detail with reference to the accompanying drawings.

First Exemplary Embodiment

<figref idrefs="DRAWINGS">FIGS. 1-4</figref> describe an inkjet head and a relationship between the inkjet head, a driving circuit thereof, and an inkjet printer, according to the embodiment. Following is an overall description, concurrent with a description of a configuration of each respective component, with reference to the drawings.

<figref idrefs="DRAWINGS">FIG. 1</figref> depicts a view illustrating an inkjet head according to the embodiment; while <figref idrefs="DRAWINGS">FIG. 2</figref> depicts an oblique cutaway view of the inkjet head depicted in <figref idrefs="DRAWINGS">FIG. 1</figref>.

An inkjet head <b>1000</b> takes a format of performing a recording by causing heat in response to an electrical signal, applying the heat to an ink, and causing a film boiling in the ink to occur. As depicted in <figref idrefs="DRAWINGS">FIG. 2</figref>, the inkjet head <b>1000</b> includes a recording element unit <b>1001</b> and an ink supply member <b>1500</b> of an ink supply unit <b>1002</b>. Reference numeral <b>1800</b> denotes an ink tank, wherein each respective color of ink is accumulated.

<figref idrefs="DRAWINGS">FIG. 3</figref> depicts an oblique cutaway view of the recording element unit <b>1001</b> shown in <figref idrefs="DRAWINGS">FIG. 2</figref>. The recording element unit <b>1001</b> includes a recording element board <b>1100</b>, a first plate <b>1200</b>, an electric wiring board <b>1300</b>, a second plate <b>1400</b>, and a filter member <b>1600</b>.

<figref idrefs="DRAWINGS">FIG. 4A</figref> depicts a view illustrating a configuration of the recording element board <b>1100</b>. <figref idrefs="DRAWINGS">FIG. 4B</figref> depicts a cross-section view of a section labeled A-A in <figref idrefs="DRAWINGS">FIG. 4A</figref>.

The recording element board <b>1100</b> is formed of a silicon wafer <b>1108</b>, with a thickness of between about 0.5 mm and 1 mm, and an electrothermal transducer, i.e., a heater, from a thin film, for example. As an ink passage, an ink supply opening <b>1101</b> is formed from a penetrating opening, as depicted in <figref idrefs="DRAWINGS">FIG. 4B</figref>, and an electrothermal transducer <b>1102</b> is arrayed in a staggered fashion, one each along either side of the ink supply opening <b>1101</b>. The electrothermal transducer <b>1102</b> and an aluminum or other electrical wiring are formed by a deposit technology. An electrode <b>1103</b>, as depicted in <figref idrefs="DRAWINGS">FIG. 4A</figref>, is included in order to supply electricity to the electrical wiring. The ink supply opening <b>1101</b> is formed by using a crystal orientation of the silicon wafer <b>1108</b> to perform an anisotropic etching. If a wafer surface has a crystal orientation of [100] (indicating Miller indices), and a thickness has a crystal orientation of [111] (indicating Miller indices), an alkali anisotropic etching, i.e., KOH, TMAH, or hydrazine, among other possibilities, will proceed at an angle of approximately 54.7 degrees. Employing the anisotropic etching method forms the ink supply opening <b>1101</b> with a desired depth.

As depicted in <figref idrefs="DRAWINGS">FIG. 4B</figref>, a nozzle plate <b>1110</b> is positioned atop the silicon wafer <b>1108</b>, and an ink passage <b>1104</b>, a nozzle <b>1105</b>, and a bubbling chamber <b>1107</b> are formed through photolithography. The nozzle <b>1105</b> is placed such that it is in opposition to the electrothermal transducer <b>1102</b>. The ink that is supplied via the ink supply opening <b>1101</b> is heated and made to bubble by the heat of the electrothermal transducer <b>1102</b>, and discharged via each respective nozzle <b>1105</b>.

A first plate <b>1200</b> is formed from aluminum oxide (Al₂O₃) between 0.5 mm and 10 mm in thickness, for example. The raw material of the first plate <b>1200</b> is not limited to aluminum oxide. It may be made from any material possessing a coefficient of linear expansion that is equivalent to the coefficient of linear expansion of the material of the recording element board <b>1100</b>, and a coefficient of heat conductivity that is equivalent to, or higher than, the coefficient of heat conductivity of the recording element board <b>1100</b>. The raw material of the first plate <b>1200</b> may be any of silicon (Si), aluminum nitride (AlN), zirconia, Silicon Nitride (si₃N₄), silicon carbide (SiC), molybdenum (Mo), or tungsten (W), for example. An ink supply opening <b>1201</b> is formed in the first plate <b>1200</b>, in order to supply the ink to the recording element board <b>1100</b>, wherein the ink supply opening <b>1101</b> corresponds to the ink supply opening <b>1201</b>, and the recording element board <b>1100</b> is fitted and locked in place with a high degree of positional precision vis-à-vis the first plate <b>1200</b>. It is desirable that an adhesive material that is used therefore have a low degree of viscosity, a thin adhesive layer, which forms a contact surface, a comparatively large degree of hardness after setting, and be ink-repellent, for example. It is desirable that the adhesive be a thermosetting adhesive, composed primarily of an epoxy resin, or a dual ultraviolet setting thermosetting adhesive, with the adhesive layer of not more than 50 <img id="CUSTOM-CHARACTER-00001" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />m in thickness, for example. The first plate <b>1200</b> possesses an X-directional reference <b>1204</b>, a Y-directional reference <b>1205</b>, and a Z-directional reference <b>1206</b>, which serve as a criterion for determining a position.

The recording element boards <b>1100</b> (<b>1100</b><i>a </i>through <b>100</b><i>d</i>) are positioned in a staggered form on the first plate <b>1200</b>, making wide printing with a single color possible, as depicted in <figref idrefs="DRAWINGS">FIG. 1</figref> and <figref idrefs="DRAWINGS">FIG. 2</figref>. For example, a length of a nozzle group, one inch plus α, positions the four recording element boards <b>1100</b><i>a</i>, <b>1100</b><i>b</i>, <b>1100</b><i>c</i>, and <b>1100</b><i>d</i>, in a staggered form, allowing printing across a four-inch width. An edge portion of the respective nozzle groups of the recording element boards forms a region L wherein the edge portions of the nozzle groups of the recording element boards that contact one another in a staggered arrangement overlap in a direction of a print. Accordingly, a gap is prevented from occurring in the print region formed by each respective recording element board. For example, overlapped areas <b>1109</b><i>a </i>and <b>1109</b><i>b </i>are respectively formed in a nozzle group <b>1106</b><i>a </i>and a nozzle group <b>1106</b><i>b. </i>

The electric wiring board <b>1300</b> depicted in <figref idrefs="DRAWINGS">FIG. 3</figref> applies an electric signal to cause the recording element board <b>1100</b> to discharge the ink. The electric wiring board <b>1300</b> possesses four of an aperture unit <b>1303</b> into which are embedded the recording element board <b>1100</b>, and the second plate <b>1400</b> is fastened to the back. The electric wiring board <b>1300</b> also possesses an electrode terminal <b>1302</b> that corresponds to the electrode <b>1103</b>, as depicted in <figref idrefs="DRAWINGS">FIG. 4A</figref>, of the recording element board <b>1100</b>, as well as a signal input terminal <b>1301</b>, which is positioned at the wire terminal, in order to receive the electrical signal from a main body of the inkjet printer. The electric wiring board <b>1300</b> and the recording element board <b>1100</b> are connected electrically to one another. The connection method might be, for example, employing a gold wire (not shown) to connect the electrode <b>1103</b> of the recording element board <b>1100</b> to the electrode terminal <b>1302</b> of the electric wiring board <b>1300</b> via a wire bonding technology. As a raw material of the electric wiring board <b>1300</b>, a dual layer flexible wiring board might be used, for example, with an upper surface covered with a polyimide film.

The second plate <b>1400</b> is formed from an SUS board with a thickness of about between 0.5 mm and 1 mm, for example. A raw material of the second plate <b>1400</b> is not limited to the SUS, and any material may be used that possesses ink repellency and a suitable flatness. The second plate <b>1400</b> possesses the recording element board <b>1100</b> and an aperture <b>1402</b> into which the recording element board <b>1100</b> is embedded, and the second plate <b>1400</b> is fastened to the first plate <b>1200</b>. A channel unit that is formed from the aperture <b>1402</b> of the second plate <b>1400</b> and a side of the recording element board <b>1100</b> is filled with a first sealing material <b>1304</b>, as depicted in <figref idrefs="DRAWINGS">FIG. 1</figref>, which seals an electrical mounting unit of the electric wiring board <b>1300</b>. The electrode <b>1103</b>, as depicted in <figref idrefs="DRAWINGS">FIG. 4A</figref>, of the recording element board is sealed with a second sealing material <b>1305</b>, as depicted in <figref idrefs="DRAWINGS">FIG. 1</figref>, which protects an electrical connection component from corrosion by ink or an exterior shock. The ink supply opening <b>1201</b> that is on the back side of the first plate <b>1200</b> has a filter material <b>1600</b>, as depicted in <figref idrefs="DRAWINGS">FIG. 3</figref>, adhesively fastened thereto, in order to remove a foreign substance that may be mixed in with the ink.

The ink supply member <b>1500</b> depicted in <figref idrefs="DRAWINGS">FIG. 2</figref> may be formed from a resin cast mold, and is equipped with a common ink chamber <b>1501</b> and a Z-directional reference <b>1502</b>, for example. The Z reference <b>1502</b> determines the position of the recording element unit <b>1001</b> and fastens the recording element unit <b>1001</b> in place, as well as serving as a Z reference of the inkjet head <b>1000</b>.

As depicted in <figref idrefs="DRAWINGS">FIG. 2</figref>, the inkjet head <b>1000</b> is formed by integrating the recording element unit <b>1001</b> with the ink supply member <b>1500</b>. A flange of the common ink chamber <b>1501</b> of the ink supply member <b>1500</b> and the recording element unit <b>1001</b> are sealed with a third sealing material <b>1503</b>, making the common ink chamber <b>1501</b> airtight. The Z reference <b>1206</b> of the recording element unit <b>1001</b> has a position determined within the Z reference <b>1502</b> of the ink supply member <b>1500</b>, and is fastened with a screw <b>1900</b> or other device, for example. It is desirable that the third sealing material <b>1503</b> be ink-repellent, harden at room temperature, and be sufficiently flexible to resist a linear expansion differential between a varying type of material. The signal input terminal <b>1301</b> of the recording element unit <b>1001</b> has a position determined on the back of the ink supply member <b>1500</b>, for example, and fastened in place.

<figref idrefs="DRAWINGS">FIG. 5A</figref> and <figref idrefs="DRAWINGS">FIG. 5B</figref> depict a cross-section view and a diagram, respectively, of the recording element unit <b>1001</b> of the inkjet head according to the embodiment, with the nozzle omitted.

A silicon wafer <b>100</b>, which corresponds to the silicon wafer <b>1108</b> depicted in <figref idrefs="DRAWINGS">FIG. 4B</figref>, has a temperature detection element, i.e., a sensor, that is formed from a thin film resistance, that may be composed of Al, Pt, Ti, TiN, TiSi, Ta, TaN, TaCr, Cr, CrSiN, or W, among other possibilities, via a thermal storage layer <b>101</b> that may be composed of a thermal oxide film SiO2, among other possibilities. Reference numeral <b>131</b> denotes a wire, which may be made of aluminum, among other possibilities, for connecting to each respective temperature sensor <b>102</b>. Numeral <b>133</b> denotes a common wire that connects in common to the temperature sensor <b>102</b>. An electrothermal transducer <b>104</b>, of TaSiN or other material, which corresponds to the electrothermal transducer <b>1102</b> depicted in <figref idrefs="DRAWINGS">FIG. 4B</figref>, is formed of a passivation film <b>105</b> that is made of SiO₂or other substance, by way of the interlayer insulation film. A protective film <b>106</b>, which may be made of Ta or other substance, is formed by being layered in a high density with a semiconductor process, in order to reduce an effect of cavitation.

The temperature sensor <b>102</b>, which is formed by the thin film resistance, is positioned directly below each respective electrothermal transducer <b>104</b>, separate and isolated therefrom. The wire <b>131</b> and the common wire <b>133</b>, to which are connected each respective temperature sensor <b>102</b>, are configured as a component of a detection circuit that obtains the temperature data that is detected by each respective temperature sensor <b>102</b>.

The silicon wafer <b>100</b> is formed with an aluminum wire that connects a control circuit that is formed of the electrothermal transducer <b>104</b> and the silicon wafer <b>100</b>, via the thermal storage layer <b>101</b> that may be composed of a thermal oxide film SiO2, among other possibilities. The protective film <b>106</b>, which may be made of Ta or other substance, is formed by being layered in a high density with a semiconductor process, in order to reduce an effect of cavitation of the electrothermal transducer, atop the electrothermal transducer <b>104</b>, of TaSiN or other material, the passivation film <b>105</b> that is made of SiO₂or other substance, by way of the interlayer insulation film <b>103</b>. It is possible to form a film and pattern the temperature sensor <b>102</b> that is formed of the thin film resistance and the wire <b>131</b> and the common wire <b>133</b>, of aluminum or other material, for the connecting wiring, atop the thermal storage layer <b>101</b>, and thus, production thereof is possible without a significant alteration of an existing production process. A significant advantage is thus obtained in an industrial manufacturing term as well.

<figref idrefs="DRAWINGS">FIG. 6</figref> depicts a view illustrating a form of the temperature sensor according to another embodiment of the present invention. Components thereof that are similar to the components in <figref idrefs="DRAWINGS">FIG. 5</figref> are depicted with a same reference number.

In the example depicted in <figref idrefs="DRAWINGS">FIG. 5B</figref>, a square temperature sensor <b>102</b> is placed directly below the electrothermal transducer <b>104</b>. In <figref idrefs="DRAWINGS">FIG. 6</figref>, by contrast, a serpentine temperature sensor <b>102</b><i>a </i>is placed directly below the electrothermal transducer <b>104</b>. The square temperature sensor <b>102</b> in <figref idrefs="DRAWINGS">FIG. 5B</figref> may be formed in a flat manner of the level form of the electrothermal transducer <b>104</b>, by way of the interlayer insulation film <b>103</b>. Consequently, an advantage is gained in that the ink discharge from each respective nozzle is more stable. It is possible, by contrast, to significantly set the value of the resistance of the temperature sensor with the serpentine temperature <b>102</b><i>a </i>in <figref idrefs="DRAWINGS">FIG. 6</figref>, by contrast, and thus, gain an advantage of being able to detect a slight temperature change in the electrothermal transducer with a high degree of precision.

<figref idrefs="DRAWINGS">FIG. 7</figref> is a block diagram describing a driving circuit and a temperature detection circuit of the electrothermal transducers (hereinafter, heaters) of the inkjet head according to the first embodiment of the present invention.

A segment includes the heater <b>104</b>, a switching element <b>903</b> that drives the heater <b>104</b>, and an AND gate <b>904</b>, which performs an AND operation on a selection signal and an on/off signal. A total of 640 segments are partitioned in 20 groups, numbered from 0 to 19, with each group being configured of 32 segments. A configuration example of being driven in 32 blocks by 20 groups is depicted. Block Enable, or BLE, assembly of wires <b>905</b> is configured of 32-bit BLE signals, numbered BLE<b>0</b> through BLE<b>31</b>, which each enable one segment within each respective group, i.e., simultaneously enabling 20 segments, and each of 32-bit BLE signals is wired in common to each respective group, resulting in a total of 32 blocks, with each block constituted of 20 heaters, one for each group. A driving data assembly of wires <b>906</b>, which is configured of 20-bit on/off signals corresponding to data to be printed, numbered ID<b>0</b> through ID<b>19</b>, each of the 20-bit on/off signals is wired separately to each respective group. A decoder <b>907</b> takes and decodes a five-bit block number from a latch <b>909</b>, and instigates the BLE<b>0</b> through BLE<b>31</b>. An AND gate <b>908</b> determines a length of a pulse that is supplied to each heater <b>104</b>, as well as the timing by which the pulse is supplied. The AND gate <b>908</b> performs an AND operation on a Heat Enable, or HE, signal of the supplied pulse and the print data, and generates the data signal ID<b>0</b> through ID<b>19</b>. The latch <b>909</b> and the shift register <b>910</b> obtain and store a serial data Idata, which is synchronized to CLK, supplied, serially forwarded to, and stored in, the shift register <b>901</b>. Hence, the data that is stored in the shift register <b>910</b> is stored in the latch <b>909</b>, using a latch signal LT that is initially outputted by the next driving block. Consequently, the corresponding heater <b>104</b> is in fact driven by the timing at which the forwarding of the data to be printed in the next block is performed, according to the initially forwarded data.

The data that is forwarded to the shift register <b>910</b> contains the block number, 0 through 31, that is driven by the data, as well as the driving data, i.e., the print data, of the heater <b>104</b> that is driven in the block, a selection data of an analog switch <b>916</b>, and a switch data of the temperature sensor <b>102</b>. The switch data selects the temperature sensor <b>102</b> as pertains to a temperature detection circuit <b>911</b>, to be described hereinafter. Upon receipt of the number data that specifies the driving block, the decoder <b>907</b> decodes the BLE<b>0</b> through BLE<b>31</b>, and enables one heater <b>104</b> within the 32 heaters <b>104</b> within each respective group, that is to say, a total of 20 heaters <b>104</b>, simultaneously. Meanwhile, the 20-bit print data ID<b>0</b> through ID<b>19</b> having a pulsewidth corresponding to that of the HE pulse are supplied to each respective corresponding heater <b>104</b>, which are then driven.

Initially, the 0 block, i.e., BLE=0, is driven, following in sequence by block <b>1</b>, block, <b>2</b> block <b>3</b>, and so on, until block <b>31</b>, i.e., BLE=31, is finished, whereupon all nozzles on all of the recording element boards, if the inkjet head is configured of a plurality of recording element boards, execute a print by discharging the ink in accordance with the print data ID<b>0</b> through ID<b>19</b>.

Included in the temperature detection circuit <b>911</b> is a switching element <b>913</b> at one terminal of the temperature sensor <b>102</b>, which is connected to the wire <b>131</b>, and controls an on/off setting thereto. Another terminal of the temperature sensor <b>102</b> is connected to the common wire <b>133</b> of each respective group, to which in turn is connected a plurality of the temperature sensors <b>102</b>. A segment is configured of an AND gate <b>914</b> that performs an AND operation on a Block Enable (BLE) and a PTEN on/off signal, the switching element <b>913</b>, and the temperature sensor <b>102</b>, which form a temperature sensor group. In the present circumstance, the temperature sensor group possesses <b>640</b> of the temperature sensor <b>102</b>, corresponding to the number of the heater <b>104</b>. The 640 temperature sensors <b>102</b> are partitioned in 20 groups of 32 elements each, as per the driving circuit <b>901</b>, forming a 32×20 matrix, with output enabled from each respective sensor. A sensor BLE assembly of wires <b>918</b> is configured of 32-bit BLE signals, numbered BLE<b>0</b> through BLE<b>31</b>, which each enable one temperature sensor <b>102</b> within each respective group, and are wired in common to each respective group. A sensor data assembly of wires <b>919</b> is configured of 20-bit BLE signals, numbered sensor data SENSOR DATA<b>0</b> through SENSOR DATA<b>19</b>, which each enable one group out of the 20 groups, and are wired separately to each respective group.

Within each group, a constant current source <b>915</b>, which maintains a constant electric current, and an analog switch <b>916</b>, which switches the output of each respective temperature sensor <b>102</b>, are connected to each group. A reference current source <b>921</b> controls the value of the current of the constant current source <b>915</b>. A control circuit that controls the switching element <b>913</b> and the analog switch <b>916</b> is configured of a decoder <b>920</b>, which takes a sensor block number and instigates the sensor block enabling number BLE<b>0</b> through BLE<b>31</b>, and a decoder <b>917</b>, which takes the temperature sensor BLE<b>0</b> through BLE<b>31</b> and instigates the group enabling number sensor data SENSOR DATA<b>0</b> through SENSOR DATA<b>19</b>.

The sensor block number that is forwarded to the serial register <b>910</b> and latched in the latch <b>909</b> is received in the Idata, and all 20 of the switching elements <b>913</b> that are affiliated with the block that is enabled by the sensor BLE<b>0</b> through BLE<b>31</b> are driven to an ON state. A similarly forwarded temperature sensor group number is also received, and the analog switch <b>916</b>, which is enabled by the group enabling number sensor data DATA<b>0</b> through DATA<b>19</b> that are output by the decoder <b>917</b>, is selected. An output of single temperature sensor <b>102</b>, which is affiliated with the enabled group of the enabled block, is selected. The temperature data from the selected temperature sensor <b>102</b> is synchronized with the signal PTEN, and output as a voltage signal via an output terminal SEN.

Thus, the output of each respective temperature sensor <b>102</b> is selected by controlling the switching element <b>913</b>, which selects an output of each temperature sensor <b>102</b>, and the analog switch <b>916</b>, which selects each respective group. Installing the analog switch <b>916</b> in such a fashion allows reducing the number of wires and terminals, as it will be unnecessary to have wires that directly extract the detected signal from each individual sensor of each respective temperature sensor group.

<figref idrefs="DRAWINGS">FIG. 8</figref> is a timing diagram describing an example of a timing chart of driving the heaters <b>104</b> and a control signal for obtaining the temperature data from the temperature sensor <b>102</b>.

The temperature that is detected by the temperature sensor <b>102</b> becomes a peak temperature approximately 1.2 <img id="CUSTOM-CHARACTER-00002" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec after the timing (“te” in block <b>0</b>) of the cessation of the driving of the heater <b>104</b>. If the length of the pulse that is supplied to the heater <b>104</b>, i.e., the length of the HE pulse, is 0.8 <img id="CUSTOM-CHARACTER-00003" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec, then the peak temperature of the heater appears 2 <img id="CUSTOM-CHARACTER-00004" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec after the timing (“t<b>0</b>” in block <b>0</b>) of the commencement of the pulse supply. In a case that a plurality of nozzles are being driven, they would typically be driven in a time-divisional fashion, although a circumstance may arise wherein conditions may dictate a time division interval of 2 <img id="CUSTOM-CHARACTER-00005" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec or less. In such a circumstance, it would not be possible to obtain the peak temperature value of the heater that is being driven by the block. Consequently, it is necessary to detect the peak temperature of the heater that is driven by the successive block while the block that is driven thereafter is being enabled, as depicted in <figref idrefs="DRAWINGS">FIG. 8</figref>, which shows an example of detecting the temperature of the heater that is driven in block <b>0</b>, by setting the sensor BLE signal to “0” (BLE<b>0</b> is high level) when the heaters <b>104</b> of the succeeding block <b>1</b> are enabled.

Thus, the driving of the heaters via the driving circuit <b>901</b> and the temperature detection operation via the temperature sensor <b>102</b> are not simultaneously operated. Consequently, when focusing on the temperature sensor <b>102</b> that is targeted for inspection, the temperature of the heater is detected within the enabling time of a block other than the block in which the heater is driven, by enabling the control signal of the sensor BLE and the sensor data SENSOR DATA, i.e., by enabling the analog switch <b>916</b>. <figref idrefs="DRAWINGS">FIG. 8</figref> depicts a situation wherein the peak temperature value is obtained at 2 <img id="CUSTOM-CHARACTER-00006" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec (tp) after the commencement of heating of the heater, and the time division interval td of the driving of the heater is also 2 <img id="CUSTOM-CHARACTER-00007" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec.

<figref idrefs="DRAWINGS">FIG. 8</figref> depicts a timing wherein the sensor data is SENSOR DATA<b>0</b>, that is to say, the temperature of the heater <b>104</b> of group <b>0</b> is detected. For example, when detecting the output of the temperature sensor <b>102</b> corresponding to the heater <b>104</b> that is enabled in block <b>0</b>, i.e., BLE<b>0</b>, of the heater <b>104</b> of group <b>0</b>, the temperature of the heater is measured by the temperature sensor <b>102</b> prior to driving the heater <b>104</b>, at the peak temperature thereof, and before and after an inflection point. The reason for doing so will be described in detail hereinafter, with reference to <figref idrefs="DRAWINGS">FIG. 9</figref>.

Thus, the timing by which the temperature of the heater is regulated so as to allow accurate identification of ink discharge malfunctions, even if the temperature detection attributes of the temperature sensor <b>102</b> vary with misalignment during manufacture or over the passage of time thereafter.

<figref idrefs="DRAWINGS">FIG. 9</figref> depicts a graph explaining a change in an output value of a temperature sensor, both when the inkjet head properly discharges ink, and with each respective discharge fault, when a 20V pulse is applied for 0.80 <img id="CUSTOM-CHARACTER-00008" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec to the heater <b>104</b> for which the initial temperature is 25 C, the thickness of the interlayer insulation film <b>103</b> is 0.95 <img id="CUSTOM-CHARACTER-00009" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />m, and the resistance is 360 ohms. The change in temperature that <figref idrefs="DRAWINGS">FIG. 9</figref> depicts is that which results after an ink discharge operation has been performed once through.

Reference numeral <b>990</b> denotes a temperature profile when ink has been properly discharged. Numeral <b>991</b> denotes the temperature profile when a discharge fault occurs as a result of bubbles being trapped within the nozzle. Numeral <b>992</b> denotes the temperature profile when a discharge fault occurs as a result of an ink refill not being performed properly, due to impurities accumulating in the ink passage. Numeral <b>993</b> denotes the temperature profile when a discharge fault occurs as a result of ink adhering to the surface of the nozzle. Numeral <b>994</b> denotes the temperature profile when ink cannot be properly discharged as a result of impurities blocking the nozzle.

The ink discharge malfunction <b>991</b> is caused by small bubbles aggregating into larger bubbles, through a variety of causes. In such a situation, the heat generated by the heater <b>104</b> is not transmitted due to the bubbles in the ink passage. Hence, the heat cannot escape, as per the upper part of <figref idrefs="DRAWINGS">FIG. 5A</figref>, and is instead accumulated in the thermal storage layer <b>101</b>. Accordingly, the temperature detected by the temperature sensor <b>102</b> will be higher at any time than that detected during proper ink discharge.

The ink discharge malfunction <b>992</b> is caused by impurities accumulating in the ink passage, such that ink refill is not completed in time for the next heat enable signal (HE) to be applied. In such a circumstance, there will be ink to one degree or another on the protect film <b>106</b>. Consequently, a greater amount of heat is transmitted to the ink than would be transmitted during an ink discharge malfunction caused by bubbles. Hence, while the temperature detected by the temperature sensor <b>102</b> will be higher at any time than that detected during proper ink discharge, it will also be lower than that detected during the ink discharge malfunction <b>991</b> caused by bubbles.

In the ink discharge malfunction <b>993</b> due to ink adhering to the surface of the nozzle, upon ink jetting, a tail portion of an ink droplet becomes a droplet itself as a result of the surface tension of the ink, and a satellite or mist of ink results, rather than the kind of ink droplet that is necessary for regular printing. When the ink satellite or mist adheres to the periphery of the nozzle, it interferes with the ink discharge, and may result in such ink application malfunctions (abnormal wetting) as a misalignment of the placement of the ink droplet. In such a circumstance, ink that adheres to the nozzle surface is pulled up into the nozzle as the meniscus retreats therein. Consequently, the timing whereby the ink contacts the protect film <b>106</b> comes faster than under normal circumstances. As a result, while the temperature detected by the temperature sensor <b>102</b> will follow the same profile as that for a proper ink discharge until the ink that adheres to the nozzle surface contacts the protect film <b>106</b>, the temperature so detected declines at a more rapid timing, i.e., before inflection point, than under normal circumstances. Particularly, a curve denoted by numeral <b>993</b> is lower than a curve denoted by numeral <b>990</b> after the timing T<b>2</b>.

In the ink discharge malfunction <b>994</b>, an ink discharge cannot be properly performed because impurities clog the nozzle, or bubbles are created and grow therein. In such a circumstance, the bubbles grow and shrink, unlike that which arises from trapped bubbles or insufficient refilling. Given, however, that the nozzle is obstructed, wholly or partially, the bubbles expand into the common ink chamber. Consequently, the timing whereby the ink contacts the protect film <b>106</b> through refilling comes later than under the normal circumstances. Hence, the timing for cooling by ink refilled from the common ink chamber will vary from that under the normal circumstances. Such timing is defined as “during refilling.”

Accordingly, the timing T<b>1</b> prior to applying the driving pulse, the timing T<b>2</b> when the peak temperature is reached, the timing T<b>3</b> that is approximately 2 <img id="CUSTOM-CHARACTER-00010" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s before timing Ti and after timing T<b>2</b>, and the timing T<b>4</b> that is approximately 2 <img id="CUSTOM-CHARACTER-00011" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s after timing Ti, are measured by the temperature sensor <b>102</b>. The timing Ti indicates a timing when the ink contacts the protect film <b>106</b> and a timing corresponding to an inflection point of a temperature change in unit time. A timing TA indicates a timing at which a driving pulse is applied. Note, the timing T<b>3</b> may be before the timing Ti and approximately 3 <img id="CUSTOM-CHARACTER-00012" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s after the timing T<b>2</b>. It is thus possible to determine with ease when ink is being discharged properly, and when there is an ink discharge malfunction.

<figref idrefs="DRAWINGS">FIG. 10</figref> depicts a graph explaining how the temperature that the temperature sensor <b>102</b> detects varies depending on the thickness of the interlayer insulation film <b>103</b>, when ink is properly discharged at an initial temperature of 25 C, and the thickness of the interlayer insulation film <b>103</b> is 0.85 <img id="CUSTOM-CHARACTER-00013" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />m, per the solid line <b>10</b><i>a</i>, and 1.35 <img id="CUSTOM-CHARACTER-00014" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />m, per the dashed line <b>10</b><i>b. </i>

As per the graph, the interval between the application of the driving pulse to the heater <b>104</b> at timing t<b>1</b> and the point when the peak temperature is reached, and the interval between the peak temperature and the point where the temperature changes as the ink is refilled, is longer when the thickness of the interlayer insulation film <b>103</b> is 1.35 <img id="CUSTOM-CHARACTER-00015" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />m, per <b>10</b><i>b, </i>than when the thickness is 0.85 <img id="CUSTOM-CHARACTER-00016" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />m, per <b>10</b><i>a. </i>Accordingly, the timing that is suited to determining whether the ink discharge is working properly or not may be misaligned depending on the thickness of the interlayer insulation film <b>103</b>. Thus, it becomes more difficult to determine accurately whether the ink discharge is working properly or not in cases where the discharge malfunction determination is made according to a fixed timing. Consequently, a recommendation is made for a process that determines whether the ink discharge is working properly or not, and which is not dependent on the thickness of the interlayer insulation film <b>103</b>, according to the embodiment.

<figref idrefs="DRAWINGS">FIG. 11</figref> depicts a view of an example full multi-inkjet printer that employs the inkjet head according to the embodiment. Reference numeral <b>2210</b> denotes a print paper feed cartridge. Numeral <b>2209</b> denotes a manual print paper feed. Conceivable paper feed protocols might include such as the Duplo protocol, wherein a paper feed roller <b>2211</b> and a paper separation pad are used to separate sheets of recording paper one at a time, as well as the lug and retard protocols. A sheet of recording paper supplied from the print paper feed cartridge <b>2210</b> or the manual print paper feed <b>2209</b> is brought into contact with the leading edge of a nip of resist rollers <b>2204</b> and <b>2205</b>, the rotation thereof being suspended. A paper advance roller <b>2211</b> is rotated slightly in the resulting state. Slack in the sheet of recording paper between the resist roller <b>2204</b> and the paper advance roller <b>2211</b> is taken up, and a misalignment in the feed direction corrected. When a photo sensor (not shown) detects that the sheet of recording paper has come into contact with the leading edge of a nip of the resist rollers <b>2204</b> and <b>2205</b>, the resist rollers <b>2204</b> and <b>2205</b> are rotated. It would be possible to print an image at a prescribed position on the sheet of recording paper by regulating the timing of the driving of the inkjet head, i.e., the driving of the heater, with the commencement of the rotation of the resist rollers <b>2204</b> and <b>2205</b> acting as a trigger thereof.

Once fed by the rotations of the resist rollers <b>2204</b> and <b>2205</b>, the sheet of recording paper is clamped by a conveyor belt <b>2006</b> and a pinch roller <b>2207</b> and <b>2208</b>. High voltage current is applied to the lower roller <b>2208</b> of the pinch roller <b>2207</b>, and the upper roller <b>2207</b> is grounded. Thus, the sheet of recording paper that passes through the pinch rollers <b>2207</b> and <b>2208</b> will absorb static electricity as it is fed along the conveyor belt <b>2206</b>. The rotation of a drive roller <b>2201</b>, which is driven by a pulse motor (not shown) that is the driving source thereof, advances the conveyor belt <b>2206</b> in moving the sheet of recording paper to the print commencement position, directly below inkjet heads <b>2221</b> through <b>2224</b>.

The conveyor belt <b>2206</b> is strung between the drive roller <b>2201</b>, a driven roller <b>2202</b>, and a pressure roller <b>2203</b>. The pressure roller <b>2203</b> is attached to an end of an arm (not shown), so as to freely rotate, and the other end of the arm is attached to a casing (not shown) that swings freely. The arm applies tension to the conveyor belt <b>2206</b> by way having a spring apply pressure thereto.

Reference numerals <b>2221</b> through <b>2224</b> denote all full-line type inkjet heads, each with a plurality of nozzles arrayed thereupon that span the width of the print region of the sheet of recording paper. In order from the upstream end of the direction of the feed of the sheet of recording paper, the heads are positioned the black head <b>2224</b>, the yellow head <b>2223</b>, the magenta head <b>2222</b>, and the cyan head <b>2221</b>, spaced at specified intervals. The inkjet heads <b>2221</b> through <b>2224</b> are attached to an inkjet head holder.

In the configuration, the sheet of recording paper is adhered to the upper surface of the conveyor belt <b>2206</b>, which feeds the sheet of recording paper as the sheet of recording paper is printed using the inkjet heads.

Reference numerals <b>2211</b> and <b>2212</b> denote a print paper discharge roller, the conveyor drive thereof is due to the rotational energy of the driven roller <b>2202</b>, by way of a transfer device (not shown). After printing, the sheet of recording paper is pinched by the print paper discharge roller and a spur <b>2211</b>, which discharge the printed sheet of recording paper to a discharge tray <b>2213</b>, where the sheets are collected. Given that the spur <b>2211</b> contacts the printed surface of the printed sheet of recording paper, the edge of the surface of the spur <b>2211</b> that contacts the sheet of recording paper is sharpened, in order to minimize a shift in the ink of the printed image.

<figref idrefs="DRAWINGS">FIG. 12</figref> is a block diagram describing an example configuration of an inkjet printer according to the embodiment. Elements of <figref idrefs="DRAWINGS">FIG. 12</figref> that are similar to elements in other figures are designated with identical reference numbers, and descriptions thereof are omitted.

A control unit <b>1220</b>, possessing a CPU <b>1230</b>, a ROM <b>1231</b> and a RAM <b>1232</b>, controls the overall operation of the printer. An inkjet head <b>1000</b> is constituted to correspond to each of the black, yellow, magenta, and cyan inks, as depicted in <figref idrefs="DRAWINGS">FIG. 11</figref>. A mechanism <b>1221</b>, wherein the configuration of each respective inkjet head is identical, contains feed mechanism for the sheet of recording paper, as well all types of sensors, such as a print paper sensor. An A/D converter <b>1222</b> receives the temperature data, i.e., the SEN signal, from the inkjet heads, and converts the SEN signal thus received into a digital value. The CPU <b>1230</b> controls the overall operation of the printer, according to a control program stored in the ROM <b>1231</b>. The RAM <b>1232</b> is used as a working area for the CPU <b>1230</b> during control processing thereby. All types of data are temporarily stored in the RAM <b>1232</b>.

The timing for determining whether the ink is being discharged properly, or whether an ink discharge malfunction has occurred, is set according to the chart for changing the timing for determining whether the ink is being discharged properly, or whether an ink discharge malfunction has occurred, as depicted in <figref idrefs="DRAWINGS">FIG. 13</figref>, in order that an ink discharge malfunction may be accurately detected, despite a misalignment during manufacture or over the passage of time thereafter.

<figref idrefs="DRAWINGS">FIG. 13</figref> is a flowchart explaining a process according to the first embodiment. The program for executing the process is stored in the ROM <b>1231</b>, and is executed under the control of the CPU <b>1230</b>.

In step S<b>101</b>, an electric current is passed through the heater <b>104</b> that corresponds to a single nozzle, prior to the determination operation, and the change in temperature resulting therefrom is measured by the corresponding temperature sensor <b>102</b>. The selection of the heater <b>104</b> that is applied current and heated and the selection of the temperature sensor <b>102</b>, are as per the description with reference to <figref idrefs="DRAWINGS">FIG. 7</figref>. The temperature data thus gathered is input into the CPU <b>1230</b> as a digital value resulting from the conversion of the SEN signal by the analog-to-digital converter <b>1222</b>. The same applies to successive temperature measurements described hereinafter.

During the interval for the measurement of the heat transfer attribute of the nozzle, either the signal PTEN is output a plurality of times with a short period, with the temperature sensor data and the temperature sensor BLE signal being fixed, or else the signal PTEN is left switched on, with the digital value that corresponds to the SEN at the time being derived and stored in the RAM <b>1232</b>. It is thus possible to obtain an inkjet head temperature attribute from an initial temperature, such as depicted in <figref idrefs="DRAWINGS">FIG. 9</figref> or <figref idrefs="DRAWINGS">FIG. 14A</figref>, for example.

<figref idrefs="DRAWINGS">FIG. 14A</figref> depicts graphs explaining a measurement of a temperature attribute of the inkjet head according to the embodiment. The attributes are similar to those described with reference to <figref idrefs="DRAWINGS">FIGS. 9 and 10</figref>.

The process then proceeds to step S<b>102</b>, wherein a first order differentiation of the temperature changes that are measured in step S<b>101</b> is obtained with respect to the duration of the measurement, and the results are outputted. <figref idrefs="DRAWINGS">FIG. 14B</figref> depicts an example of the results.

Next, the process proceeds to step S<b>103</b>, wherein the first order differentiation obtained in step S<b>102</b> is further differentiated and the second order differential results of temperature changes with a time period are obtained. <figref idrefs="DRAWINGS">FIG. 14C</figref> depicts the results. Whereas the differentiations are taken in software according to the first embodiment, it would also be permissible to employ a differential calculator or other hardware device.

The process then proceeds to step S<b>104</b>, wherein the time is obtained when a value of the first order differentiation obtained in step S<b>102</b> becomes 0, and the time is obtained when a value of the second order differentiation obtained in step S<b>103</b> becomes a negative peak while the values of the first order differentiation obtained in step S<b>102</b> are negative value. The timing at which when the value of the first order differentiation becomes 0 denotes the timing at which the temperature detected by the temperature sensor <b>102</b> reaches the peak temperature. The timing wherein the values of the first order differentiation are negative and the value of the second order differentiation is at its peak value, denotes a timing Ti at when the temperature changes as the ink contacts the protect film <b>106</b>.

Then the process proceeds to step S<b>105</b>, wherein the following timings for obtaining the temperature data from the temperature sensor <b>102</b> are established: <ul><li id="ul0001-0001" num="0105">1. T<b>1</b>, the timing prior to the application of the driving pulse of the heater;</li><li id="ul0001-0002" num="0106">2. T<b>2</b>, the timing when the peak temperature, as detected in step S<b>104</b>, is reached;</li><li id="ul0001-0003" num="0107">3. Ti, the timing when the temperature of the heater changes as the ink contacts the protect film <b>106</b> after the peak temperature;</li><li id="ul0001-0004" num="0108">4. T<b>3</b>, the timing between the timings T<b>2</b> and Ti, approximately 2 <img id="CUSTOM-CHARACTER-00017" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s before the timing Ti; and</li><li id="ul0001-0005" num="0109">5. T<b>4</b>, the timing approximately 2 <img id="CUSTOM-CHARACTER-00018" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s after the timing Ti.</li></ul>

The data pertaining to each respective timing thus established is stored in the RAM <b>1232</b>.

The process proceeds to step S<b>106</b>, wherein the temperature data for each respective timing is obtained in accordance with the timing data stored in step S<b>105</b>. If the temperature data for a given heater <b>104</b> is specified, the temperature for the heater <b>104</b> is measured by the corresponding temperature sensor <b>102</b> at T<b>1</b>, that is, prior to the application of the driving pulse. This is followed by measuring the temperatures at the timings of T<b>2</b>, T<b>3</b> and T<b>4</b>.

Next, the process proceeds to step S<b>107</b>, wherein the thresholds of determination of each respective timing T<b>1</b> through T<b>4</b> are re-set, based on the temperature data measured in step S<b>101</b>, to thresholds that are more suited to the present circumstance. The temperature data pertaining to the measurement timing obtained in step S<b>105</b>, is used to establish the thresholds for determining whether or not the state of ink discharge is normal, based on the temperature data at the time. In the present circumstance, the thresholds are set to a temperature value that has a differential above or below the value that is measured at the time.

The process then proceeds to step S<b>108</b>, wherein the temperature data obtained by measurement at each respective timing in step S<b>106</b>, and the thresholds corresponding to each respective timing obtained in step S<b>107</b>, are respectively compared, and the state of each nozzle is determined.

According to the first embodiment, the timing by which the temperature data is obtained in order to determine whether an ink discharge malfunction has occurred or not is taken to be the timings T<b>1</b> through T<b>4</b>, thus allowing a determination as to whether an ink discharge malfunction at each nozzle has occurred or not at each respective timing with maximum accuracy.

The change of the timing of the measurement in order to determine whether the ink is being properly discharged or not is described as being performed during a print operation, according to the first embodiment. It would also be permissible, for example, to perform the process in the interval between the end of a print of a previous line or sequence, and the commencement of the next print. It would also be permissible to do so while performing a preliminary ink discharge process in order to refresh the ink in preparation for a print.

It would also be permissible to measure the timing of the measurement in order to determine whether the ink is being properly discharged or not, according to the first embodiment, prior to leaving the factory, and store the data as timings that are optimized for the inkjet heads in the ROM <b>1231</b> or other nonvolatile memory. It would also be permissible for the user to alter the timing of the measurement at will.

It would also be permissible to automatically update the timing of the measurement when a given amount of time period has passed after the timing of the measurement is established.

Second Exemplary Embodiment

Following is a description according to a second embodiment of the present invention, which facilitates the detection of an ink discharge malfunction with a high degree of accuracy even after misalignment during manufacture or over the passage of time thereafter. The description of such configurations as the configuration of the inkjet head and the configuration of the inkjet printer will be omitted according to the second embodiment, because they are similar to those according to the first embodiment.

<figref idrefs="DRAWINGS">FIG. 15</figref> is a flowchart explaining a process according to the second embodiment. The program for executing the process is stored in the ROM <b>1231</b>, and is executed under the control of the CPU <b>1230</b>.

Additionally, <figref idrefs="DRAWINGS">FIG. 15</figref>, steps S<b>201</b> through S<b>205</b> are similar to the processes described in <figref idrefs="DRAWINGS">FIG. 13</figref>, steps S<b>101</b> through S<b>105</b>.

In step S<b>201</b>, an electric current is passed through the heater <b>104</b> that corresponds to a single nozzle, prior to the determination operation, and the change in temperature resulting therefrom is measured by the corresponding temperature sensor <b>102</b>. The selection of the heater <b>104</b> that applies heat and drive to the nozzle and the selection of the temperature sensor <b>102</b>, are as per the description with reference to <figref idrefs="DRAWINGS">FIG. 7</figref>. The temperature data thus gathered is input into the CPU <b>1230</b> as a digital value resulting from the conversion of the SEN signal by the A/D converter <b>1222</b>. The same applies to successive temperature measurements described hereinafter.

The process proceeds to step S<b>202</b>, wherein a first order differentiation of the temperature change measured in step S<b>201</b> is obtained with respect to the duration of the measurement, and the results are outputted. The process proceeds to step S<b>203</b>, wherein a second order differentiation of results of the first order differentiation obtained in step S<b>202</b> is obtained, and the results are outputted. Whereas the differentiations are taken in software according to the second embodiment, it would also be permissible to employ a differential calculator or other hardware device.

The process then proceeds to step S<b>204</b>, wherein the time is obtained when a value of the first order differentiation obtained in step S<b>202</b> becomes zero, and the time is obtained when a value of the second order differentiation obtained in step S<b>203</b> becomes a negative peak while the values of the first order differentiation obtained in step S<b>202</b> are non-positive. The timing wherein the value of the first order differentiation becomes zero is the timing T<b>2</b> at which the temperature detected by the temperature sensor <b>102</b> reaches the peak temperature. The timing T<b>3</b> wherein the values of the first order differentiation are negative and the value of the second order differentiation is a negative peak, is when the temperature of the heater changes as the ink contacts the protect film <b>106</b>.

Next, the process proceeds to step S<b>205</b>, wherein the following timings for obtaining the temperature data from the temperature sensor <b>102</b> are established: <ul><li id="ul0002-0001" num="0124">1. T<b>1</b>, the timing prior to the application of the driving pulse of the heater;</li><li id="ul0002-0002" num="0125">2. T<b>2</b>, the timing when the peak temperature, as detected in step S<b>204</b>, is reached;</li><li id="ul0002-0003" num="0126">3. Ti, the timing when the temperature changes as the ink contacts the protect film <b>106</b> after the peak temperature;</li><li id="ul0002-0004" num="0127">4. T<b>3</b>, the timing between the timings T<b>2</b> and Ti, approximately 2 <img id="CUSTOM-CHARACTER-00019" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s before the timing Ti; and</li><li id="ul0002-0005" num="0128">5. T<b>4</b>, the timing approximately 2 <img id="CUSTOM-CHARACTER-00020" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s after the timing Ti.</li></ul>

The data pertaining to each respective timing thus established is stored in the RAM <b>1232</b>.

Thereafter, process proceeds to step S<b>206</b>, wherein the interval from a latch signal LT to the driving of, i.e., the supplying of current to, the heater <b>104</b>, is changed such that it conforms with the optimal point for determining whether or not the nozzle slated for the determination, as is calculated in step S<b>205</b>, is experiencing an ink discharge malfunction, following a prescribed period of time subsequent to the latch signal LT.

<figref idrefs="DRAWINGS">FIG. 16</figref> depicts a view illustrating a variant example of timing. It is presumed that the timing of the measurement is 7.00 <img id="CUSTOM-CHARACTER-00021" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s after the LT signal. In such a circumstance, the peak temperature and the threshold of the nozzle slated for determination are compared. It is presumed, however, that that the timing of the measurement of the peak temperature is calculated to be 8.00 <img id="CUSTOM-CHARACTER-00022" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s after the LT signal, owing to misalignment in manufacture. In such a circumstance, it is determined that a 1.00 <img id="CUSTOM-CHARACTER-00023" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s differential exists between the currently set timing of the measurement and the calculated timing of the measurement of the peak temperature. Hence, the interval between the latch signal LT and the supplying of current to the heater <b>104</b>, i.e., the time to outputting the HE signal, is hastened by 1.00 <img id="CUSTOM-CHARACTER-00024" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s. In the figure, numeral <b>1600</b> denotes a pre-alteration signal HE, and numeral <b>1601</b> denotes a post-alteration signal HE. Consequently, it is possible to measure the peak temperature 7.00 <img id="CUSTOM-CHARACTER-00025" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />s after the LT signal.

The process then proceeds to step S<b>207</b>, wherein the heat pulse signal is applied to the heater <b>104</b> at the timing that is altered in step S<b>206</b>, and the temperature data is obtained at the timing subsequent to the prescribed interval following the LT signal. The process proceeds to step S<b>208</b>, wherein the thresholds of determination of each respective timing for measurement for detecting an ink discharge malfunction are re-set, based on the temperature data measured in step S<b>201</b>, to thresholds that are more suited to the present circumstance. The process is performed similarly to the process in <figref idrefs="DRAWINGS">FIG. 13</figref>, step S<b>107</b>. The process proceeds to step S<b>209</b>, wherein the temperature data obtained by measurement at each respective timing in step S<b>207</b>, and the thresholds corresponding to each respective timing, that are obtained in step S<b>208</b>, are compared, and the state of each nozzle is determined.

While the prescribed measurement interval according to the first and second embodiments has been described in terms of only one point in time, it would be permissible to have a plurality of timings for measurement as well.

<figref idrefs="DRAWINGS">FIG. 17A</figref> and <figref idrefs="DRAWINGS">FIG. 17B</figref> depict views explaining a circumstance wherein a plurality of the measurement timings are set versus to a heater driving, according to the second embodiment.

<figref idrefs="DRAWINGS">FIG. 17A</figref> depicts an example of determining whether or not there is an ink discharge malfunction by applying a common correaction value C<b>1</b> to all of the timings for measurement T<b>2</b> through T<b>4</b>. <figref idrefs="DRAWINGS">FIG. 17B</figref> depicts a situation wherein different correaction values C<b>2</b> through C<b>4</b> are respectively set for the timings for measurement T<b>2</b> through T<b>4</b>, and determinations as to whether or not there is an ink discharge malfunction are performed by obtaining the temperature data for each respective timing for measurement T<b>2</b> through T<b>4</b> that is corrected by each respective correaction value.

According to the first and second embodiments, it would also be permissible, for example, to determining whether or not there is an ink discharge malfunction for each respective nozzle in the interval between the end of a print of a previous line or sequence, and the commencement of the next print, in addition to doing so while performing a preliminary ink discharge process in order to refresh the ink in preparation for a print.

It would also be permissible for the process of changing the timings for measurement according to the first and second embodiments to measure the temperature prior to leaving the factory, and store the data as timings of the measurement in order to determine whether the ink is being properly discharged or not that are optimized for the inkjet heads in the ROM <b>1231</b> or other nonvolatile memory.

It would also be permissible for the user to alter the timing of the measurement at will. It would also be permissible to automatically re-set the timing of the measurement when a given amount of time period has passed after the timing of the measurement is altered.

The description according to the first and second embodiments has pertained to the inkjet printer executing the inspection method that is depicted in <figref idrefs="DRAWINGS">FIGS. 13 and 15</figref>. The present invention is not limited thereto, however. It would be permissible for a dedicated inkjet head inspection device to execute the inspection method as well. The configuration of such a device would be similar to that of the inkjet printer, at least as pertains to the inkjet head driving assembly, and thus, it would be permissible to omit a conveyor assembly for sheets of recording paper, for example. A description of the configuration of the inspection device will accordingly be omitted.

Third Exemplary Embodiment

<figref idrefs="DRAWINGS">FIG. 18</figref> is a circuit diagram of an inkjet head according to the third embodiment of the present invention. The circuit diagram operates in a manner fundamentally similar to the circuit depicted in <figref idrefs="DRAWINGS">FIG. 7</figref>.

The temperature sensor <b>102</b>, which is positioned near to the electrothermal transducer (heater) <b>104</b>, is formed of the thin film resistance. A switching device <b>703</b>, which is connected to a terminal of each respective temperature sensor <b>102</b>, controls whether each respective temperature sensor <b>102</b> is on or off. The other terminal of each respective temperature sensor <b>102</b> is collectively connected to a common wiring <b>701</b>, which, in turn, supplies a given electric current from a constant current source <b>705</b>. A plurality of detection circuits <b>706</b> each output a voltage that arises from each respective temperature sensor <b>102</b>. A switching circuit <b>707</b> selects the output of the detection circuit <b>706</b>, and outputs the output thereof to a sensor output terminal <b>712</b>. A sensor control circuit <b>708</b>, controls switching on the part of the switching devices <b>703</b> and the switching circuit <b>707</b>, in order that the temperature data that is detected by each temperature sensor <b>102</b> is outputted. The detection circuit <b>706</b>, the switching circuit <b>707</b>, and the temperature sensor control circuit <b>708</b> are configured in a manner similar to that of the analog switch <b>916</b> and the decoders <b>917</b> and <b>920</b> in the example in <figref idrefs="DRAWINGS">FIG. 7</figref>.

The value of a temperature sensor output terminal <b>712</b>, which is a temperature output terminal of the temperature sensor <b>102</b> that is selected by the temperature sensor control circuit <b>708</b>, such as the analog switch, is corrected by a corrector <b>711</b> and outputted by a temperature data output terminal SEN. A heater control circuit <b>709</b> controls the switching of the switching element <b>710</b> that is connected to each respective heater <b>104</b>, synchronizing with the image data or the heat signal HE, among other possibilities, and sends power to each corresponding heater <b>104</b>. The heater control circuit <b>709</b> corresponds to the driving circuit <b>901</b> in <figref idrefs="DRAWINGS">FIG. 7</figref>.

<figref idrefs="DRAWINGS">FIG. 19A</figref> depicts a view illustrating a configuration of the inkjet head according to the third embodiment. A plurality of the inkjet head boards, chip <b>1</b> through chip <b>4</b>, are positioned atop a support unit made of aluminum or other material. The number, arrangement, or other aspect of the chips are not limited to the present embodiment. The configuration of the circuit of each respective chip is, for example, a circuit configuration such as that depicted in <figref idrefs="DRAWINGS">FIG. 7</figref> or <figref idrefs="DRAWINGS">FIG. 18</figref>.

<figref idrefs="DRAWINGS">FIG. 19B</figref> depicts a view explaining an output pertaining to an output terminal of each respective sensor, and a misalignment thereof, pertaining to the inkjet head depicted in <figref idrefs="DRAWINGS">FIG. 19A</figref>.

Each respective temperature sensor output is capable of deriving from the product of the sum of the resistance when the switching device <b>703</b> is switched on and the resistance of the temperature sensor <b>102</b>, and the electric current that is supplied via the constant current source <b>705</b>. The temperature that is detected by the temperature sensor <b>102</b> can, in turn, be derived from the temperature coefficient of the resistance Rs of the temperature sensor. The factors in the misalignment of the temperature sensor output of each unit can be categorized as electrical or thermal. The following are possible factors in misalignment of the electrical variety: <ul><li id="ul0003-0001" num="0146">1. Misalignment of the electrical current in the constant current source <b>705</b>;</li><li id="ul0003-0002" num="0147">2. Misalignment of the resistance Rs, owing to the size, film thickness, or quality of the temperature sensor <b>102</b>; and</li><li id="ul0003-0003" num="0148">3. Misalignment of the electrical current from the constant current source <b>705</b>, owing to the resistance when the switching device <b>703</b> is switched on and the resistance of the wiring.</li></ul>

The following are possible factors in misalignment of the thermal variety: <ul><li id="ul0004-0001" num="0150">1. Misalignment owing to the thickness, or quality of the interlayer insulation film <b>103</b>; and</li><li id="ul0004-0002" num="0151">2. Misalignment of temperature caused by resistance affected by the size or shape of the heater <b>104</b>.</li></ul>

Other possible types of electrical and thermal misalignment include: <ul><li id="ul0005-0001" num="0153">1. Misalignment Caused by the Positional misalignment of the temperature sensors on the chip;</li><li id="ul0005-0002" num="0154">2. Misalignment between chips, arising from the positions of the inkjet head boards within the inkjet head; and</li><li id="ul0005-0003" num="0155">3. Other Generalized Electrical or Thermal misalignment in addition to the misalignment between inkjet head boards.</li></ul>

It is of course important to eliminate electrical and thermal misalignment. Efforts are being made in this regard in the design and production processes. Misalignment of these sorts inevitably occur in manufacturing, however, and the presence of such misalignment makes accurate detection of temperature data impossible.

<figref idrefs="DRAWINGS">FIG. 20</figref> is a flowchart describing a calibration process of the inkjet head according to the third embodiment. The program for executing the process is stored in the ROM <b>1231</b> of the control unit <b>1220</b>, and is executed under the control of the CPU <b>1230</b>.

In step S<b>901</b>, i.e., the first process, the output of the temperature sensor <b>102</b> is read out, with the heater <b>104</b> switched off. In step S<b>902</b>, i.e., the second process, the output of the temperature sensor <b>102</b> is read out, with the heater <b>104</b> switched on. The correaction process in step S<b>903</b> reads in the values read out in steps S<b>901</b> and S<b>902</b> to derive the electrical and thermal misalignment therefrom. The correaction process in step S<b>903</b> corresponds to the process pertaining to process by the corrector <b>711</b> in <figref idrefs="DRAWINGS">FIG. 18</figref>. The temperature data outputted from the temperature sensor <b>102</b> is corrected, in accordance with the electrical and thermal misalignment so derived. Thus corrected, the temperature data is outputted as the temperature data that is detected by way of the temperature sensor <b>102</b>, per step S<b>904</b>. While the corrector <b>711</b> is depicted as being contained in the inkjet head configuration according to the embodiment, the present invention is not limited thereto. The control unit <b>1220</b> may include the corrector <b>711</b>.

Each respective nozzle of the inkjet head comprises a heater <b>104</b> and a temperature sensor <b>102</b>, according to the embodiment. Ink is discharged via the nozzle when the ink in the nozzle is heated as a result of electric current being passed through the heater <b>104</b>.

In step S<b>901</b>, according to the third embodiment, the above described electrical misalignment, i.e., misalignment caused by the positional misalignment of sensors in each chip, and misalignment caused by the positional misalignment of chips within the inkjet head, arising from the electrical misalignment between chips, is detected. Such misalignment is detected within the range of the electrical misalignment, centering on a reference value Ta, which is the temperature that is detected by the temperature sensor <b>102</b> when the heater <b>104</b> is off; hereinafter “room temperature reference value.” The electrical misalignment in each respective nozzle thus detected is stored in the corrector <b>711</b>.

In step S<b>902</b>, the misalignment between the thermal misalignment of the inkjet heads, i.e., misalignment caused by the positional misalignment of the chips, and misalignment caused by the positional misalignment of chips within the inkjet head, is detected centering on a target reference value Tg, the temperature that is detected by the temperature sensor <b>102</b> when the heater <b>104</b> is on; hereinafter “increased temperature reference value”.

The overall misalignment, in accordance with the electrical misalignment Teoff and the thermal misalignment K of each respective nozzle, is stored in the corrector <b>711</b>. It would be permissible for the value thus stored to be the measured value Tt as well.

Thus, the electrical and thermal misalignments are corrected and the reference value is determined in order to judge the state of the inkjet heads.

Reading out the correaction value for correcting electrical and thermal misalignment allows the manufacturer to easily perform a calibration at time of shipment from the factory. It would also allow a user to perform a calibration during use, for example, by automatically obtaining the corrected values when the device is being activated, or between sheets of printing paper, during a print job. It is thus possible to detect the temperature for each respective nozzle within the inkjet head with a high degree of precision, even if changes arise in the inkjet head attributes due to electrical or thermal misalignment.

<figref idrefs="DRAWINGS">FIG. 21</figref> depicts a view explaining the electrical misalignment and an overall misalignment that are stored in a correaction unit, according to the third embodiment.

Following is a description of an example using the room temperature reference value Ta, immediately prior to the ink discharge, and the target increased temperature reference value Tg, which is assumed to be reached a given amount of time after the ink discharge.

While the room temperature reference value Ta is presumed to be 10 C, 25 C, or 40 C, it is permissible to set the value even more finely. While the increased temperature reference value Tg is described as the target temperature value at a point in time a designated amount of time following the ink discharge drive, it is permissible to set the increased temperature reference value for more points in time. The increased temperature reference value Tg is established by the voltage and the pulsewidth that are applied to the heater <b>104</b>.

In step S<b>901</b>, the temperature data that is detected by the temperature sensor <b>102</b> that corresponds to each respective nozzle is read out in a constant temperature state, for example, the room temperature reference value Ta=25C. The difference between the temperature data and the room temperature reference value Ta is the electrical misalignment TEoff.

In step S<b>902</b>, a pulse of 18V and 0.8 <img id="CUSTOM-CHARACTER-00026" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec pulsewidth is applied to the heater <b>104</b> of the inkjet head whereupon the temperature sensor <b>102</b> is positioned, by way of the interlayer insulation film <b>103</b>, as depicted in <figref idrefs="DRAWINGS">FIG. 5A</figref>. After 2 <img id="CUSTOM-CHARACTER-00027" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec from the timing at which the heater <b>104</b> is switched on, the inkjet head temperature measurement value Tt is detected and stored for a given condition, for example, a normal ink discharge state.

As is already clear, the measurement value Tt is an overall misalignment, containing the electrical misalignment TEoff and the thermal misalignment K, the latter being detected by the temperature sensor <b>102</b> when electric current is applied to the heater <b>104</b>.

It is desirable that the thermal misalignment K and the electrical misalignment TEoff that are measured and derived be stored in an EEPROM (not shown) or other nonvolatile storage, rather than the RAM <b>1232</b>.

As per the foregoing, the electrical misalignment TEoff and the thermal misalignment K of each respective nozzle are stored into a data table, and used as the correaction values when overwriting the data on the actually measured temperature. It is thus possible to obtain the temperature data for each respective nozzle of the inkjet head with a high degree of precision.

Using the temperature data or the threshold data when performing the determination of the ink discharge malfunction detection on a per nozzle basis, as well as the temperature data for controlling the change in ink discharge quantity that occurs on a per nozzle basis, allows detecting the ink discharge malfunction and controlling the ink discharge quantity with a high degree of precision.

According to the third embodiments, the time required to measure a one-inch chip with a 1200 dpi resolution, for example, with two points being measured every 2 <img id="CUSTOM-CHARACTER-00028" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec, is 1200 dots×2 <img id="CUSTOM-CHARACTER-00029" he="3.13mm" wi="1.02mm" file="US07690751-20100406-P00001.TIF" alt="custom character" img-content="character" img-format="tif" />sec=4.8 msec. Hence, it is possible to measure and store the temperature of each respective nozzle in a very short period of time, even with inkjet heads that contain a large number of nozzles, and to calibrate the temperature data for each respective nozzle based on the measured temperatures.

The electrical misalignment TEoff that is obtained in step S<b>901</b>, i.e., the first process, is dependent on the electrical misalignment that has such causes as the resistance of the wiring or the attributes of the circuits, as pertains to the calibration when changing the temperature condition. Our own review indicates that it is possible to reuse the 25 C measured value for the electrical misalignment TEoff. It would also be permissible, however, to perform another measurement using the foregoing method, and store and calibrate the result, taking into account the temperature attribute of the electrical misalignment TEoff.

A variety of combinations are possible regarding the setting of the timing of the reading out of the first and second processes, with regard to the embodiment. It would be permissible, for example, for the manufacturer to carry out the first process at time of shipment, and for the second process to be carried out while in use by the end user, for example, automatically, either when the device is activated or between sheets of printing paper, during a print job. It would also be permissible for both the first and second processes to be carried out by the manufacturer, at time of shipment, as well as while in use by the end user.

With regard to the description of the electrical and thermal misalignment, only one or the other of the plus or the minus misalignment vis-à-vis the reference value has been represented. Naturally, however, it would be possible to handle both the plus and minus misalignment in similar fashion, yielding a similar effect.

According to the third embodiments, the output of the temperature sensor <b>102</b> is read out while the heater <b>104</b> of the inkjet head is off. Then the output of the temperature sensor <b>102</b> is read out while the heater is on. It is possible to use the values thus read out to correct the output of the temperature sensor.

Hence, it is possible to obtain the temperature data with a high degree of precision, corrected for both electrical and thermal misalignment, when detecting the temperature in the vicinity of the heater on a per nozzle basis, and using the data in determining the ink discharge state of the inkjet head, or in controlling the ink discharge quantity.

A line-type of inkjet head is particularly capable of offering an inkjet head with high quality image and product quality, while also being inexpensive, reliable, and packaged in a small form factor, as well as an inkjet print apparatus that employs the inkjet head. The resulting industrial and manufacturing effects are thus highly significant.

Further, according to the third embodiment, it is possible to perform the calibration with ease on the part of the manufacturer, at time of shipment. It is also possible to obtain the corrective value while in use by the end user, for example, automatically, either when the device is activated or between sheets of printing paper, during a print job. Consequently, it is possible to detect the temperature data with a high degree of precision, even if there are electrical or thermal changes in the attributes of the inkjet head. It is thus possible to perform a detection of an ink discharge malfunction, or to perform a control of a quantity of ink discharge, with a high degree of precision.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims priority from Japanese Patent Application No. 2006-169381, filed Jun. 19, 2006, which is hereby incorporated by reference herein in its entirety.